1. Field of the Invention
The present invention relates to a semiconductor device having a transistor circuit and a bleeder resistance circuit, and a method of manufacturing the semiconductor device. More particularly, the present invention relates to reduction of fluctuation in resistance value of a bleeder resistor.
2. Description of the Related Art
In power supply ICs, polysilicon is commonly used for bleeder resistors, and shift in resistance value of the bleeder resistors has critical influence on the overall characteristics of the IC. Metal film placed above a bleeder resistance circuit is not used as an interconnect, but is used mostly to stabilize the resistance value of the bleeder resistor by being connected in a manner that gives the metal film the same electric potential as that of the bleeder resistor to stabilize an electric field in its vicinity (JP09-321229A). A conductor below the bleeder resistor is also connected in a manner that gives the conductor the same electric potential as that of the bleeder resistor.
Semiconductor devices that have a transistor circuit and a bleeder resistance circuit employ a film that is used commonly to form metal interconnect as it is for the metal film placed above the bleeder resistance circuit. The metal film accordingly has a structure of anti-reflection film/interconnect film/barrier metal film (JP2006-222410A).
The anti-reflection film, which is the topmost layer and is formed of a-Si, TiN, TiW, or the like, is sometimes omitted according to necessity. The interconnect film below the anti-reflection film is formed of aluminum containing a few percents of Si or Cu. The barrier metal film below the interconnect film is a TiN/Ti laminated film or a TiW film.
The barrier metal film has high stress as well as high barrier property, and causes the resistance value of the underlying polysilicon film which forms the bleeder resistor to fluctuate by means of stress. Arranging the barrier metal film above the bleeder resistor could therefore make the voltage division ratio of the bleeder resistor deviate from the correct value.